Under certain driving conditions and situations, a driver may cause the vehicle to undergo a hard turn, a quick turn, or a series of hard and quick turns. Such conditions can be experienced during high speed maneuvers which may occur on freeway entrance ramps, merging lanes and the like. Quick maneuvers also occur to avoid accidents or objects. During such maneuvers, the vehicle body tends to elevate on one side and lower on the opposite side very suddenly. This condition is referred to as vehicle body roll. High profile vehicles such as trucks, sports utility vehicles, vans and the like experience roll conditions more readily than lower profile vehicles.
Many different types of vehicle suspension and stabilizer systems have been used for both passenger comfort and driving stability. Primary suspension system components operate to control a single wheel assembly movement relative to the vehicle frame and can include springs and/or dampers provide spring force to suspend the vehicle body. The primary suspension system components further provide damping resistance to suspended body motion, but only a minimal resistance to vehicle body roll. Roll stabilizer systems are often cross-connected from one wheel assembly to the other and provide spring force to return the vehicle body to a neutral position or condition when forces from sudden vehicle movements have cause the body to lean one direction or the other. Accordingly, stabilizer systems operate to return the vehicle body from a roll condition to a neutral condition.
A variety of roll stabilizer systems are known. Torsion stabilizer systems utilize a stabilizer bar, bar bushings and links in series attached to the primary suspension system and vehicle frame. The stabilizer bar acts as a torsion spring to return the vehicle body to a neutral condition when forces have caused to body to lean or roll. Several types of linear roll stabilizer systems are also known connected across the vehicle between primary suspension components. In a single compensating stabilizer system one anti-roll compensator is provided and operates as a tension and compression spring. The anti-roll compensator is attached to the primary suspension with one bell crank on each control arm. In a dual compensating linear stabilizer system two anti-roll compensators are provided. The compensators work as a pair of tension springs and are under no load in compression. The anti-roll compensators attach to the primary suspension with two bell cranks on each control arm, with each compensator attached to an upper bell crank on one control arm and to a lower bell crank on the other control arm.
While stabilizer systems as described operate effectively to return the vehicle to a neutral condition after vehicle body roll has been experienced, known systems provide minimal roll resistance or “damping” to inhibit the initial entry of the vehicle body into a roll condition. In a torsional stabilizer system roll damping results only from compliance in the end links and bar bushings. In linear stabilizer systems, either single compensating or dual compensating stabilizer systems, some inherent roll damping results from the elastomeric spring elements. However, such damping is minimal.
To provide improved vehicle body roll damping, in the past attempts have been made to “tune” vehicle primary suspension systems. The primary suspension dampers, such as shocks and/or struts and other suspension geometry or architecture can be altered to improve roll damping. However, tuning roll damping into the primary suspension systems is limited by the suspension dampers primary functions and the suspension geometry. Generally, tuning the primary suspension system to provide greater roll resistance is achieved at the expense of vehicle ride comfort. To provide adequate roll resistance or damping may not be acceptable with known suspension system tuning, as the reduction in ride comfort is too severe.
What is needed is a roll damping system that works in conjunction with primary suspension system components and roll stabilizer systems, without compromising the performance thereof.